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Effect of selection for increased litter size on ovulation rate and embryo survival in sheep

Published online by Cambridge University Press:  24 November 2017

J.P. Hanrahan
J.P. Hanrahan*
Affiliation:
Agriculture and Food Development Authority, Belclare, Tuam, Co. Galway, Ireland
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Abstract

Variation in litter size in sheep is essentially attributable to variation in ovulation rate and embryo survival. Genetic variation in litter size, both among and within breeds, is largely attributable to variation in ovulation rate. While there is evidence for genetic differences among breeds in embryo survival the contribution of this component to within breed variation appears to be minor (Hanrahan, 1982). The impact of selection based on litter size on its component traits should reflect the relative contribution of these components to within breed variation. Data from two lines of Galway sheep, a Control line and one selected for increased prolificacy (Hanrahan and Timon, 1978), have been used to provide evidence on this point.

Details relating to the selection experiment which provided the data for the present study are in Hanrahan (1984). Briefly a flock of Galway sheep was assembled from industry sources (both pedigree and non-pedigree) between 1963 and 1965.

Type
Sheep production
Information
Proceedings of the British Society of Animal Production (1972) , Volume 1990 , March 1990 , pp. 32
Copyright
Copyright © The British Society of Animal Production 1990

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References

Hanrahan, J.P., (1982). Proc. 2nd Wld. Congr. Genetics Applied to Livestock Prod. V: 193–201.Google Scholar
Hanrahan, J.P., (1984). Proc. 2nd Congress on Sheep and Beef Cattle Breeding pp 483–493.Google Scholar
Hanrahan, J.P. and Timon, V.M., (1978). Anim. Prod. 26: 372.Google Scholar